Churchill provide and install Anti-carbonation treatments in order to prevent the carbonation process. We supply two systems for carbonation prevention these being Elastomer and Acrylic coloured or clear coating systems and the market leading liquid silica product EverCrete Vetrofluid®
The process of carbonation naturally occurs in untreated concrete that is exposed to the elements. As soon as the concrete is exposed to the air, the process of carbonation can begin, carbon dioxide slowly penetrates the surface of the concrete where it reacts with moisture in the pores and calcium hydroxide (which is one of the compounds in concrete) to form calcium carbonate.
As carbon dioxide meets the pore water, a dilute carbolic acid is created which acts to reduces the concrete's natural alkalinity.
Carbonation of concrete does not occur in parallel lines but takes the easiest path toward the embedded reinforcement. Poorly compacted concrete and construction joints are two common pathways for accelerated carbonation.
Ca(OH)2 + CO2 -> CaCO3 + H2O
Depending upon the concrete's porosity and permeability, concrete carbonation may advance at a rate of 1mm to 5mm per year. The initial effect is a hardening of the concrete and a corresponding increase in its compressive strength. However the process of carbonation also serves to reduce the natural alkalinity of the concrete from around pH13 to pH8. This in turn results in the cement paste shrinking from around the bound aggregate and opening up minor ficias and pathways allowing oxygen and moisture to pass through the concrete. As carbon dioxide travels deeper into the concrete and approaches the depth of embedded steel, the passivating layer around the reinforcement is lost by the process of carbonation, exposing the steel to the corrosive effects of air and water.
Churchill are approved applicators of many of the leading manufacturers Anti-Carbonation coating systems such as Sikas Sikagard 680S and Sika 550W Elastic.
Churchill are also an approved licensed applicator of the Evercrete Vetrofluid system.